Your door has torsion springs if one or two thick coils sit on a bar across the wall above the opening, and extension springs if long springs stretch above each horizontal track. Both kinds counterbalance the door so it weighs very little by the time your hands or the opener move it.
They differ in where they sit, how they store energy, and what happens when one breaks, and those differences decide how the door gets repaired and which openers it can take.
Either way, a spring holds the most energy when the door is down, which is why everything attached to it, from the lift cables to the bottom brackets, is dangerous to loosen. Identifying your springs is a look-only job; spring replacement is work for a technician.
How a torsion system lifts the door
A torsion system twists one or two springs around a steel tube above the door, and that twist turns cable drums that reel in the lift cables as the door rises.
The springs slide over a torsion tube that spans the header. One end of each spring is anchored to a center bearing plate on the wall; the other carries a winding cone, which a technician turns with winding bars to load it. As the door closes, the cables unwind from the drums on both ends of the tube and the springs twist tighter.
Because the springs ride on the tube, a broken torsion spring stays put. DASMA, the trade association for door and opener makers, points out in its inspection checklist that a shaft-mounted spring is contained by design, one reason most sectional doors since the 1990s use torsion.
A torsion break announces itself: one sharp bang, then an open space of about two inches between the halves of one coil when you look up at the tube.
How an extension system lifts the door
An extension system stretches a pair of long springs mounted over the horizontal tracks, left and right, and pulleys turn that stretch into lift.
Each spring hooks to a hanger toward the back of the track at one end and carries a pulley at the other. From the bottom bracket, the lift cable climbs over the pulleys to a fixed anchor, so closing the door pulls the springs longer, and opening it lets them contract and help raise the door.
The weak point is a break. A stretched spring that snaps, or a pulley or cable that fails under load, can send metal flying across the garage. That is why every extension spring needs a safety cable running down its middle and secured at each end, and DASMA’s checklist asks inspectors to confirm exactly that.
Extension springs always work in pairs, one on each side, and DASMA’s color code table assumes the two springs share the door’s weight between them.
Tell them apart in two minutes
With the door closed and no ladder or tool, look above the opening for a bar with coils, which means torsion, or along the horizontal tracks for long springs, which means extension.
- Close the door and stand inside, clear of its path. The springs are loaded and easy to see in this position.
- Look at the wall just above the opening. A bar across the width of the door with one or two thick coils on it, and a cable drum at each end, is a torsion system.
- If the bar is there but smooth, with no coils showing, the springs are inside the tube. That is the TorqueMaster design covered on our Wayne Dalton page.
- If there is no bar, follow the horizontal tracks back toward the ceiling. Long springs running parallel to each track, with pulleys at their front ends, are extension springs.
- Look for the safety cable. On an extension door, a thin cable should pass straight through the middle of each spring.
- Count the springs. A torsion door may have one or two; an extension door should always have two.
- If the whole door swings out as one slab, it is a one-piece tilt-up with its own spring hardware, and our tilt-up door guide covers it.
Torsion and extension springs side by side
Torsion springs sit on a tube, come singly or in pairs, stay put when they break and allow a wall-mount opener; extension springs always come in pairs, need safety cables and rule a wall-mount out.
| Torsion | Extension | |
|---|---|---|
| Where it sits | On a tube above the door opening | Above each horizontal track |
| How many | One or two | Two, one per side |
| How it stores energy | Twisting around the tube | Stretching lengthwise |
| If it breaks | The tube keeps it in place | A safety cable must catch it |
| Sign of a break | A bang and a two-inch split in one coil | A spring hanging loose, a slack cable and a heavy door |
| What its paint mark means | Wire diameter | The door weight a pair is built for |
| Wall-mount opener | Can be fitted | Cannot be fitted |
What the paint stripe on a spring tells you
The dab of color near the end of a spring is a code that marks wire diameter on a torsion spring and the door weight a pair is built for on extension springs.
DASMA publishes the official color codes. On torsion springs, the color marks wire diameter, cycling through a fixed list from thin wire to thick. On extension springs, it marks the door weight the springs are built for, in 10-pound steps from 50 to 300 pounds, with a note that two springs are needed for that weight.
The code is only a partial ID. DASMA warns that it says nothing about inside diameter, length or material, that colors should be backed up by measuring the spring and weighing the door, and that homeowners should not use the chart to replace springs. Treat a color you can see as a clue to pass along, not a shopping list.
Faded or rusty springs may show no color at all. And a door that has gained weight from paint or added insulation may have outgrown its original springs, a mismatch DASMA lists among the reasons springs fail early.
Which system is safer, and what to check today
Torsion is the safer design because the tube contains a break, but an extension door with intact safety cables is a sound system too.
From the floor, look for those cables on both sides. If one is missing, frayed or anchored at only one end, keep people clear of the spring’s path and have it added soon. Fitting one means working on loaded spring hardware, so leave it to a technician.
On either system, leave the bottom brackets, lift cables and winding cones alone, since they carry the spring’s load whenever the door is down. If a cable hangs slack or has jumped its drum, our cable and drum repair page explains what comes next.
Converting extension springs to torsion
Converting swaps the whole counterbalance, not just the springs, and it earns its keep when you want a wall-mount opener, better containment, or springs matched to a heavier new door.
The job removes both extension springs with their pulleys and cables, then installs a torsion tube on end bearing plates, a center bearing plate, cable drums, new lift cables and springs sized to the door’s measured weight. The tube and drums need room above the opening, so that space gets measured before anything is planned.
A conversion also makes a wall-mount opener possible, because those units work only by turning a torsion bar. Our comparison of belt, chain and wall-mount openers covers that decision, and the spring replacement cost guide explains how spring jobs are priced.
A light single door in good balance, with sound safety cables, can keep running on extension springs for years. Spending on a conversion makes the most sense when it rides along with another goal.
Damp garages wear down both types
Moisture shortens the life of torsion and extension springs alike, because rust eats into the wire wherever the spring sits.
DASMA’s sheet on spring cycle life explains why: rust reduces the working area of the wire, and corrosion pits give fatigue cracks a place to start. It also advises keeping the door closed where possible in climates with frequent precipitation, since an open door exposes the springs to moisture and swings in temperature.
That advice fits a Portland garage through the rainy months. For how cycle ratings turn into years, and why some springs quit early, see our guide to how long garage door springs last.